Rotorcraft, such as helicopters, employ rotor blades to generate lift. Specifically, rotorcraft typically include a mast that is coupled to a power plant (e.g., a jet engine and transmission assembly), and the rotor blades are coupled to the mast by way of a rotor hub. Rotation of the mast about a mast axis causes corresponding rotation of the rotor blades about the mast axis, thereby generating lift.
To enhance control and stability, rotorcraft are often provided with articulatable rotor blades. One common mode of articulation, typically referred to as “flapping,” involves pivoting a rotor blade relative to the rotor hub about a horizontal flap axis. Another common mode of articulation, typically referred to as “feathering,” involves pitching a rotor blade relative to the rotor hub about a longitudinal feather axis. Other modes of articulation, such as lead-lag articulation, are also commonly used.
When flight testing a rotorcraft with articulatable rotor blades, it is often desirable to know the position of each rotor blade throughout the flight test, including the flap angle of each rotor blade and the feather angle of each rotor blade. Therefore, sensors have been installed on the exterior surface of the rotor hub to collect rotor blade position data. However, the installation of such sensors typically requires making unrepairable modifications (e.g., drilling and taping holes) to the rotor hub, and can be time consuming/expensive. Furthermore, being on the exterior surface of the rotor hub exposes the sensors to the elements, thereby requiring frequent repairs, and raises concerns about sensor components becoming disconnected from the rotor hub and coming into contact with sensitive components of the rotorcraft.
Accordingly, those skilled in the art continue with research and development efforts in the field of rotor blade position monitoring.